Question 1

A 50-year-old woman complains that in the past few months she has had little energy,has frequently felt chilled,and has noticed excessive hair loss when she washes her hair.During the physical examination,her blood pressure registers at 105/85 mm Hg,her pulse is slow,and her physician notes dry,cool skin with puffiness of the face and arms.A preliminary diagnosis of primary hypothyroidism is made.The primary reason for the elevated diastolic pressure is:

A)Pulmonary congestion.
B)Increased peripheral resistance.
C)Decreased cardiac output.
D)Low catecholamine levels.
E)Increased blood volume.

Accepted Answer

D

Question 2

Graves' disease is due to an autoantibody that binds to and activates the TSH receptor.This interaction would primarily increase which second messenger in the thyroid epithelial cells? A)Ca⁺⁺ B)Activated signal transducer and activator of transcription (STAT) C)Phosphatidylinositol 3-kinase (PI3K) D)Cyclic guanosine monophosphate (cGMP) E)Cyclic adenosine monophosphate (cAMP)

Accepted Answer

The TSH receptor activation in thyroid epithelial cells leads to the activation of adenylyl cyclase, which increases the formation of cyclic adenosine monophosphate (cAMP) from ATP. The increase in cAMP then activates protein kinase A (PKA), which plays a critical role in thyroid hormone synthesis and secretion. In Graves' disease, the autoantibody binds to the TSH receptor, leading to uncontrolled activation of the receptor and excessive thyroid hormone production, which is why increasing cAMP levels is the primary mechanism implicated in Graves' disease.

Question 3

Peripheral deiodinases can have which effect on T₄? A)Activation B)Deactivation C)No effect; theyuse only T₃ as substrate D)Activation and deactivation

Accepted Answer

Peripheral deiodinases can both activate and deactivate thyroid hormones by removing iodine atoms from the outer or inner ring of the hormone molecule, respectively. This process can convert the prohormone thyroxine (T4) into the active form triiodothyronine (T3) or into reverse T3 (rT3), which is inactive.

Question 4

Secondary hyperthyroidism due to a pituitary tumor would be associated with the following histophysiological characteristics of the thyroid gland (in relation to normal):&#10;A)Increased iodine uptake at 24 hours&#10;B)Increased colloid&#10;C)Tall columnar thyroid epithelium&#10;D)Decreased thyroglobulin endocytosis&#10;E)Lowered organification of iodide

Accepted Answer

The answer of Secondary hyperthyroidism due to a pituitary tumor...

Question 5

A 50-year-old woman complains that in the past few months she has had little energy,has frequently felt chilled,and has noticed excessive hair loss when she washes her hair.During the physical examination,her blood pressure registers at 105/85 mm Hg,her pulse is slow,and her physician notes dry,cool skin with puffiness of the face and arms.A preliminary diagnosis of primary hypothyroidism is made.The primary reason for the elevated diastolic pressure is:

A)Pulmonary congestion.
B)Increased peripheral resistance.
C)Decreased cardiac output.
D)Low catecholamine levels.
E)Increased blood volume.

Accepted Answer

In hypothyroidism, there is a decrease in thyroid hormone levels, which leads to a decreased metabolic rate and increased peripheral resistance. This increased peripheral resistance can cause an elevation in diastolic blood pressure.

Question 6

Although pregnant women do not typically exhibit hyperthyroidism,maternal total T₄ levels increase during pregnancy.This benign increase in total T₄ is due to: A)Increased synthesis of thyroid hormone-binding globulin (TBG). B)Increased pituitary deiodinase activity. C)Decreased placental deiodinase activity. D)Resistance to thyroid hormone receptor signaling. E)Decreased excretion of thyroid hormone by the kidneys.

Accepted Answer

During pregnancy, there is an increase in estrogen levels that stimulate the liver to produce higher levels of thyroid hormone-binding globulin (TBG). TBG is a protein that binds to thyroid hormones and transports them in the bloodstream. This increase in TBG leads to an increase in total T₄ levels in the bloodstream, but typically not an increase in active thyroid hormone (free T4 and free T3). This increase in TBG levels is a benign and normal adaptation during pregnancy.

Question 7

Which of the following proteins is found only at the basolateral side of thyroid epithelium? A)Na⁺-I^- symporter B)Pendrin C)Megalin D)Iodotyrosine deiodinase E)Thyroid peroxidase

Accepted Answer

The Na⁺-I^- symporter is specifically located at the basolateral membrane of thyroid follicular cells, where it facilitates the uptake of iodide from the bloodstream into the cells.

Question 8

A primary way by which T₃ increases oxygen consumption and causes heat to be generated (metabolic thermogenesis)in most cells in the body is through increasing the levels of: A)Myosin heavy chain $\alpha$ B)Glucose transporter 4 (GLUT-4). C)Uncoupling proteins. D)Nicotinamide adenine dinucleotide phosphate (NADP)oxidase. E)Epithelial sodium channel (ENaC).

Accepted Answer

Uncoupling proteins increase metabolic thermogenesis by uncoupling the electron transport chain from ATP synthesis, which generates heat instead of ATP. Myosin heavy chain, glucose transporter 4, nicotinamide adenine dinucleotide phosphate oxidase, and epithelial sodium channel do not directly increase metabolic thermogenesis.

Question 9

The thyroid hormone receptor is most like which of the following?&#10;A)Adrenergic receptor&#10;B)Insulin receptor&#10;C)Growth hormone receptor&#10;D)Estrogen receptor&#10;E)Follicle-stimulating hormone (FSH)receptor

Accepted Answer

The thyroid hormone receptor (THR) belongs to the nuclear receptor family, which also includes the estrogen receptor (ER). Both THR and ER are transcription factors that bind to DNA and regulate gene expression. Adrenergic receptors, insulin receptors, growth hormone receptors, and FSH receptors are all membrane-bound receptors that activate different signaling pathways upon ligand binding. Therefore, D is the best choice as it belongs to the same family of receptors and shares similarities in function and structure with Thyroid hormone receptors.

Question 10

Organification defect specifically concerns the inability of the thyroid to covalently bind iodide to tyrosine residues in the colloid.This reaction is performed by:&#10;A)Thyroid peroxidase.&#10;B)The sodium-iodide transporter.&#10;C)The TSH receptor.&#10;D)Iodotyrosine deiodinases.&#10;E)Thyroglobulin.

Accepted Answer

The process of iodide binding to tyrosine residues in the colloid is performed by thyroid peroxidase. The sodium-iodide transporter and the TSH receptor are involved in the uptake and regulation of iodide by the thyroid gland. Iodotyrosine deiodinases are involved in the breakdown of iodotyrosine molecules. Thyroglobulin is a protein that serves as the precursor to thyroid hormones but is not directly involved in the iodide-tyrosine binding process.

Deck 42: The Thyroid Gland